1. Technical Field
The present invention relates generally to acidic and alkaline/oxidative and reductive potential water (ORP water) and to methods of electrolyzing saline solutions. More particularly, the present invention relates to a method and apparatus for producing negative and positive ORP water, and the water so produced, for use in sterilization, decontamination, disinfection, skin cleansing, and wound healing catalysis.
2. Background Art
The production of super-oxidized water is an electrochemical, or oxidation-reduction process. This is commonly referred to as an electrolytic or redox reaction in which electrical energy is used to produce chemical change in an aqueous solution. Electrical energy is introduced into and transported through water by the conduction of electrical charge from one point to another in the form of an electrical current. In order for the electrical current arise and subsist there must be charge carriers in the water, and there must be a force that makes the carriers move. The charge carriers can be electrons, as in the case of metal and semiconductors, or they can be positive and negative ions in the case of solutions.
It is difficult to force electrical energy, or current, through pure water since it is not a charge carrier and is not ionic in and of itself. Absolutely pure water, while theoretically simple is, as a practical matter, virtually impossible to obtain. Hence, water in the form we commonly encounter it can and does conduct electrical energy, or current, due to the presence of dissolved ions. The greater the concentration of dissolved ions, the greater the ability to conduct current and the ability to produce a chemical change in the solution.
Since water is never pure it can contain numerous dissolved substances. It invariably contains trace amounts of H3O+ and OH− from the dissociation of water. It can also contain dissolved gases, such as CO2 and N2 that can also be reactants. Water also contains various anions and cations. As is well known, the H2O molecule is polar; that is, it has an unequal charge distribution. This is due to the molecular structure and the unequal attraction for electrons exerted by the oxygen and hydrogen atoms comprising the molecule. This polarity significantly enhances water's ability to dissolve numerous substances, including ionic compounds such as sodium chloride or salt.
Molecules of water can either be oxidized to O2 by the removal of electrons or reduced to H2 by the addition of electrons. Therefore water must always be considered a possible reactant. Typical reactions occur at either the cathode or the anode.
At the cathode reduction must occur. Many different reactions are possible however the following two reactions are the most likely:2H2O+2e−→H2(gas)+2OH−2H3O+2e−→H2(gas)+2H2O
There are several other possible reactions at the cathode, none of which are easy to predict. It is necessary to consider which reactant is most easily reduced and which is reduced most rapidly. The strongest oxidizing agent is not necessarily the fastest. Complications may arise when electric current is very large and the concentration of the reactants is very small.
In the presence of NaCl other reactions are to be considered, such as the evolution of chlorine and hydrogen gas and the production of OH−. The OH− or hydroxyl ion can cause significant increases in pH. In the electrolysis of NaCl, solutions show that OH− accumulates around the cathode. Cations move toward the cathode and anions toward the anode.
At the anode oxidation must occur. The most common reaction in the presence of aqueous NaCl gives rise to chlorine gas.2 Cl−−2e−→Cl2(gas)
The overall reaction during the electrolysis of aqueous NaCl solutions shows the concentration of chlorine decreasing and the concentration of OH− increasing. This condition in turn leads to other reactions and subsequent products. Chlorine gas is partly dissolved in the solution, and reacts to produce hypochlorous acid according to the following equation.Cl2+H2O→HClO and HCl
The resulting hydrochloric acid, HCl, can cause a significant drop in pH. There is also the possibility that the formation of HCl gives rise to other reactions simultaneously, but to an unknown degree. The production of atomic oxygen is possible; however due to the instability it is not present for long or in high concentration. This reactivity can give rise to other products such as oxygen gas, hydrogen peroxide, and ozone.
Combining the foregoing reactions and the resulting products and varying the process inputs and conditions, such as the amount and type of current, type and concentration of dissolved ions, and water purity, will give rise to water of varying characteristics.
All of the above-described reactions, when allowed to occur under controlled and optimal conditions, can result in the production of water that contains oxidized species resulting in something termed “super-oxidized water.” Super-oxidized water may have varying characteristics, including either high or low pH, varying chlorine and chlorine compound content, and varying degrees of oxygen and oxygen-containing compounds.
The most easily quantifiable characteristic of super-oxidized water is its pH. Depending upon the configuration of the electrolytic cell, high pH water can be produced in the cathode chamber and low pH water can be produced in the anode chamber. These can be referred to as anode or cathode water. Low pH (acidic) anode water also has chlorine present in various forms; i.e., chlorine gas, chloride ion, hydrochloric acid, or hypochlorous acid. Oxygen in various forms can also be present. The alkaline cathode water may have hydrogen gas present along with sodium ion. The process water streams from these two electrolytic cells or chambers can be separated and analyzed.
Work performed in Japan has shown that each of the two types of water produced have unique properties. One of these properties is referred to as oxidation-reduction potential (ORP). This potential can be quantified using the standard technique of measuring the electrical potential in millivolts relative to a standard reference silver/silver chloride electrode. ORPs of approximately 1000 mV have been measured. Optical absorption spectra and electron spin resonance have showed the presence of hypochlorous acid.
It has long been known in the general art of sterilization that heat, filtration, radiation, and chemicals may be employed to remove unwanted microorganisms. However, only recently have developments in the art of electrolysis provided an alternative method of microbial disinfection and sterilization. Relatively recently, apparatus have been devised to optimize the conditions that favor the production of certain end products, including both cathode and anode water of varying ORP and residual chlorine content. Super-oxidized water has a limited shelf life and decreasing activity over time. Data shows that ORP water may be effective when used in sterilization, decontamination, disinfection, skin cleansing, and wound healing catalysis.
Relevant prior art includes U.S. Pat. No. 5,932,171 to Malchesky, issued Aug. 3, 1999, which discloses a sterilization apparatus utilizing catholyte and anolyte solutions produced by electrolysis of water. The apparatus includes a tray with an article receiving area, such that an article to be microbially decontaminated is positioned in the receiving area and a microbe blocking lid is closed over the article. A water electrolysis apparatus receives water, splits the water into two separate streams that pass respectively through an anode chamber and a cathode chamber, and exposes the streams to an electric field that results in the production of a catholyte solution for cleaning and an anolyte solution for sterilization. The anolyte and catholyte are selectively circulated through the article receiving area by a pump to clean and microbially decontaminate the external surfaces and internal passages of an article located therein. The anolyte or deactivated anolyte provides a sterile rinse solution. A reagent dispensing well receives an ampule or the like. The ampule contains internal compartments which are selectively accessed or opened to dispense detergent concentrate and/or sterilant concentrate reagents into the circulating anolyte and catholyte solutions. A water treatment apparatus dispenses either a salt or a cleaning agent into the water received from the source to vary the electrolysis reaction or to form a cleaning solution to clean and flush the electrolysis apparatus, respectively.
U.S. Pat. No. 6,171,551 to Malchesky, et al., issued Jan. 9, 2001 teaches a method of and apparatus for electrolytically synthesizing peracetic acid and other oxidants. The electrolysis unit has an ion selective barrier for separating an anodic chamber from a cathodic chamber. An electrolyte within the unit includes a precursor, such as potassium acetate, or acetic acid. A positive potential is applied to an anode within the anodic chamber, resulting in the generation of a variety of shorter and longer lived oxidizing species, such as peracetic acid, hydrogen peroxide, and ozone. In one preferred embodiment, a solution containing the oxidizing species is transported to a site where articles, such as medical instruments, are to be decontaminated. The oxidizing species are generated as needed, avoiding the need to store hazardous decontaminants.
U.S. Pat. No. 5,507,932 to Robinson, issued Apr. 16, 1996, teaches an apparatus for electrolyzing fluids. The device ostensibly produces electrolyzed fluids that are Particularly suited for treating physiological materials such as whole blood, plasma, or cell isolates in order to reduce the effect of harmful microorganisms. A container holds the fluid and a power supply provides a source of electrical current to an anode and a cathode positioned within the container. The anode comprises a base material selected from titanium and niobium. An outer layer of platinum is bonded to the base. The anode comprises a cylindrical shape. The cathode is also connected to the power supply and comprises titanium and has a substantially cylindrical shape. The cathode is positioned concentrically in relation to the anode. The spacing between the cathode and the anode is not greater than a preferred amount. Moreover, the voltage potential between the cathode and the anode is not greater than a preferred amount.
Finally, and most closely related to the present invention, U.S. Pat. No. 6,296,744 to Djeiranishvili et al, teaches an apparatus for the electrochemical treatment of a liquid medium. The apparatus contains at least one midstream electrolytic cell with unipolar electrodes of positive and negative polarity, which are connected to a source of continuous electrical current and positioned on opposite sides of a semi-permeable diaphragm or membrane which divides the cell into anode and cathode electrode chambers. The chambers have pipelines attached to their nozzles. The pipelines include a feed pipe for the liquid medium being treated, a cathodic outlet pipe with a discharge point for carrying the liquid medium away from the cathode chamber, an anode outlet pipe for carrying the liquid medium from the anode chamber into the catalytic reactor for breaking down active chlorine, an exit line connected to the reactor, and a discharge point for carrying the liquid medium away to the place of collection.
While it is well known to utilize an ion selective barrier between the anode and cathode chambers of an electrolysis unit, to date it is not known to provide a supply of flowing ionic solutions in a chamber intermediate the anode and cathode chambers to facilitate the production of oxidative reduction potential (ORP) water.